There is known an apparatus for applying gas-thermal coatings to workpieces in the form of bodies of revolution (cf., catalog of the firm "Wear Control Technology" published on Sept. 8, 1981 in Losanna, Switzerland and has the title "Modular Equipment for Automatic Coating"). This apparatus comprises a headstock with a rotation drive and a tailstock with a common center of axis. The tailstock is secured on a guide for longitudinal displacement. The same guide has a carriage secured thereon to be capable of longitudinal reciprocations.
The apparatus further includes a rod carrying a spray gun and capable of lateral reciprocations in guides secured on the carriage. The rod is provided with a clam for locking it laterally in position relative to the center axis. A workpiece in the form of a body of revolution is mounted between the tailstock and headstock. The tailstock is then brought closer to the end of the workpiece. After securing the workpiece between the centers of the tialstock and headstocks the rod carrying the spray gun is brought to a position determined by the diameter of the workpiece and present distance from the spray gun to the surface of the workpiece by moving the rod laterally. This position of the rod is locked. The rotation drive is then energized, ingredients of the coating mixture are fed to the spray gun, and the carriage executes longitudinal reciprocations preset by the production process. As the lateral position of the rod carrying the spray gun is locked, coatings can be applied only to cylindrical workpieces. When applying the coating, part of the powder-like material falls onto the guide of the tailstock to impede its travel on the guide and cause premature wear of the latter.
There is also known a machine for applying gas-thermal coatings to workpieces (cf., catalog of the firm PLASMA-TECHNIK AG, published in 1980 in Wohmen Switzerland, and has the title Weellenspritzbank Typ WSP mit Sehallschutzhaube) comprising a chamber, accommodating a headstock having a rotation drive and a tailstock with a guide capable of longitudinal travel along this guide coaxially arranged inside the chamber. The machine also includes a carriage having a drive and a guide, and capable of longitudinal reciprocations along the guide, and a rod carrying a spray gun for lateral displacement in guides secured on the carriage. The guide of the tailstock, guide of the carriage, and drive for imparting longitudinal movement to the carriage are positioned inside the chamber, whereas the guide of the tailstock is arranged under the spray gun. With doors of the chamber open the workpiece in the form of the body of revolution is clamped between the centers of the headstock and tailstock. The rod carrying the spray gun is moved laterally to a position determined by the diameter of the workpiece and preferred distance between the spray gun and surface of the workpiece. The doors of the chamber are then closed. The rotation drive for rotating the workpiece is energized. Ingredients of the material to be applied are fed to the spray gun, and the carriage executes longitudinal reciprocations according to the production program. When applying coatings to a cylindrical workpiece of continuous diameter, the lateral position of the rod carrying the spray gun remains invariable through the entire coating application cycle. When applying coatings to a workpiece of varying diameter, the rod carrying the spray gun is moved laterally to a distance equal to the difference in the workpiece radii.
Because this prior art machine is intended primarily for applying coatings to cylindrical workpieces of small diameter, and consequently of small surface area, and time of continuous operation of the spray gun and drives is relatively short. Therefore, the operability of the drives and guides functioning in the zone of high temperatures and dust released by the spray gun for a short period of time is unaffected.
However, this known machine is not capable of applying coatings to flat workpieces, as this necessitates extra motions to be executed by the spray gun and requires that the flat workpiece be secured in the chamber. In addition, application of coatings of flat workpieces having large surface areas needs a longer time of continuous operation of the spray gun, which negatively affects the functioning and reduces the service life of drives and guides present in the zone of high temperature and atmosphere of dust. Arrangement of the guide of the tailstock under the spray gun promotes penetration of powdered material being sprayed onto the guide thereby impeding the movement of the tailstock therealong and making it more susceptible to premature wear.